#define   _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>

void main() {

	float a = 1, b = 1, c = 0;
	float sum = 0;
	int i = 0;
	
	for (i = 1; i < 21; i++)
	{
		c = a;
		a = b;
	    b = c + b;
		sum = sum + b/a;
	}
	printf("%.2f\n",sum);
}